I am learning Russian.
Я учу/изучаю русский язык.
I am studying at University.
Я учусь в университете.
I teach Russian.
Я преподаю русский язык.
I teach Russian to the students.
Я преподаю русский язык студентам.
I teach my son how to drive a car.
Я учу сына водить машину.
I am learning to drive a car.
Я учусь водить (машину).
Where did you learn Russian?
Где ты научился русскому языку?
Who taught you Russian?
Кто научил тебя русскому языку?
As for further examples and differences between all those words, I think quite a long essay could be dedicated to that. Let me just present some points.
Both words mean to teach. However, when you're talking about a teacher's job/position, you use преподавать.
Я учу детей математике. I teach math to the kids. (might not be my job per se)
Я преподаю математику в школе. I teach math at school. (That's my job)
Again, both words mean to teach. But the latter is perfective, meaning that it denotes completion of the teaching process.
Я учил его считать. I taught him how to count (but I don't know if he learnt)
Я научил его считать. I taught him how to count and he mastered it.
This word is usually used with trades/skills.
Пилотов обучают с помощью тренировочных симуляторов. Pilots are trained by simulators.
Изучать means to study, in all senses. You can closely study a problem (изучать проблему), you can study a subject (изучать предмет). When you say Я изучаю математику, it means that math is most likely one of your main subjects.
Means to learn (completely). For example.
Я выучил это стихотворение наизусть. I learnt this poem by heart.
Я учил английский. I studies English (means the process, not the result/completion)
Я выучил английский. I learnt English ( mastered it to some degree, denotes completion)
As I said, much more can be said about these verbs. If you pick any two and ask a separate question, it would be easier to present all the differences and nuances.